Solid-state imaging device, method of driving the same, and electronic apparatus

ABSTRACT

A solid-state imaging device includes a pixel array unit in which a plurality of imaging pixels configured to generate an image, and a plurality of phase difference detection pixels configured to perform phase difference detection are arranged, each of the plurality of phase difference detection pixels including a plurality of photoelectric conversion units, a plurality of floating diffusions configured to convert charges stored in the plurality of photoelectric conversion units into voltage, and a plurality of amplification transistors configured to amplify the converted voltage in the plurality of floating diffusions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority PatentApplication JP 2013-230219 filed Nov. 6, 2013, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND

The present disclosure relates to a solid-state imaging device, a methodof driving the solid-state imaging device, and an electronic apparatus,and particularly to a solid-state imaging device, a method of drivingthe solid-state imaging device, and an electronic apparatus that canimprove autofocusing (AF) speed and accuracy.

A solid-state imaging device that performs AF with so-called a phasedifference detection method in which an imaging pixel and a phasedifference detection pixel are provided in a pixel array unit and AF isperformed based on the amount of displacement between signals outputfrom a pair of phase difference detection pixels has been known.

In some of these solid-state imaging devices, the number of phasedifference detection pixels is increased and the AF accuracy is improvedby providing two photoelectric conversion units in a pixel (see, forexample, Japanese Patent Application Laid-open No. 2012-165070 andJapanese Patent Application Laid-open No. 2007-243744).

SUMMARY

In the phase difference detection pixel disclosed in Japanese PatentApplication Laid-open No. 2012-165070, however, because the twophotoelectric conversion units share one amplification transistor, itmay be impossible to expose and read from the two photoelectricconversion units simultaneously, which makes AF tracking capabilitieswith respect to a fast-moving subject insufficient.

On the other hand, in the phase difference detection pixel disclosed inJapanese Patent Application Laid-open No. 2007-243744, by providing acharge storage unit configured to store charges for each photoelectricconversion unit, it is possible to expose and read from the twophotoelectric conversion units simultaneously.

However, by providing a charge storage unit, the area of thephotoelectric conversion unit decreases. As a result, the sensitivity ofthe phase difference detection pixel and the AF accuracy are reduced.

The present disclosure had been made in view of the above circumstances,and it is desirable to improve the AF speed and accuracy.

According to an embodiment of the present disclosure, there is provideda solid-state imaging device, including a pixel array unit in which aplurality of imaging pixels configured to generate an image, and aplurality of phase difference detection pixels configured to performphase difference detection are arranged, each of the plurality of phasedifference detection pixels including a plurality of photoelectricconversion units, a plurality of floating diffusions configured toconvert charges stored in the plurality of photoelectric conversionunits into voltage, and a plurality of amplification transistorsconfigured to amplify the converted voltage in the plurality of floatingdiffusions.

In each of the plurality of phase difference detection pixels, at leastone of the plurality of photoelectric conversion units may share thefloating diffusion and the amplification transistor with at least one ofthe plurality of imaging pixels, which is adjacent to the phasedifference detection pixel.

The phase difference detection pixel may include a first photoelectricconversion unit and a second photoelectric conversion unit, the firstphotoelectric conversion unit may share the floating diffusion and theamplification transistor with a first imaging pixel adjacent to thephase difference detection pixel, and the second photoelectricconversion unit may share the floating diffusion and the amplificationtransistor with a second imaging pixel that is different from the firstimaging pixel and is adjacent to the phase difference detection pixel.

The phase difference detection pixel and the first imaging pixel may beincluded in one pixel sharing unit, and the second imaging pixel may beincluded in another pixel sharing unit.

According to an embodiment of the present disclosure, there is provideda method for driving a solid-state imaging device that includes a pixelarray unit in which a plurality of imaging pixels configured to generatean image, and a plurality of phase difference detection pixelsconfigured to perform phase difference detection are arranged, each ofthe plurality of phase difference detection pixels including a pluralityof photoelectric conversion units, a plurality of floating diffusionsconfigured to convert charges stored in the plurality of photoelectricconversion units into voltage, and a plurality of amplificationtransistors configured to amplify the converted voltage in the pluralityof floating diffusions, the method including storing charges in theplurality of photoelectric conversion units, and reading signalscorresponding to the charges stored in the plurality of photoelectricconversion units, by the solid-state imaging device, in the phasedifference detection pixel.

According to an embodiment of the present disclosure, there is providedan electronic apparatus, including a solid-state imaging device thatincludes a pixel array unit in which a plurality of imaging pixelsconfigured to generate an image, and a plurality of phase differencedetection pixels configured to perform phase difference detection arearranged, each of the plurality of phase difference detection pixelsincluding a plurality of photoelectric conversion units, a plurality offloating diffusions configured to convert charges stored in theplurality of photoelectric conversion units into voltage, and aplurality of amplification transistors configured to amplify theconverted voltage in the plurality of floating diffusions.

According to an embodiment of the present disclosure, a plurality of FDsconvert charges stored in the photoelectric conversion units intovoltage in the phase difference detection pixel, and a plurality ofamplification transistors amplify the voltage of the FDs.

According to an embodiment of the present disclosure, it is possible toimprove the AF speed and accuracy.

These and other objects, features and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription of best mode embodiments thereof, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration example of anelectronic apparatus including a solid-state imaging device to which anembodiment of the present disclosure is applied;

FIG. 2 is a diagram for explaining pixel arrangement;

FIG. 3 is a diagram for explaining sharing of a floating diffusion (FD)and an amplification transistor;

FIG. 4 is a plan view showing a configuration example of a pixelaccording to a first embodiment of the present disclosure;

FIG. 5 is a circuit diagram showing a configuration example of the pixelaccording to the first embodiment of the present disclosure;

FIG. 6 is a plan view showing another configuration example of the pixelaccording to the first embodiment of the present disclosure;

FIG. 7 is a circuit diagram showing another configuration example of thepixel according to the first embodiment of the present disclosure;

FIG. 8 is a plan view showing a configuration example of a pixelaccording to a second embodiment of the present disclosure;

FIG. 9 is a circuit diagram showing a configuration example of the pixelaccording to the second embodiment of the present disclosure;

FIG. 10 is a flowchart for explaining the configuration of the FD;

FIG. 11 is a flowchart for explaining the configuration of the FD;

FIG. 12 is a plan view showing a configuration example of a pixelaccording to a third embodiment of the present disclosure;

FIG. 13 is a circuit diagram showing another configuration example ofthe pixel according to the third embodiment of the present disclosure;

FIG. 14 is a plan view showing another configuration example of thepixel according to the third embodiment of the present disclosure; and

FIG. 15 is a circuit diagram showing another configuration example ofthe pixel according to the third embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be describedwith reference to the drawings.

Functional Configuration Example of Electronic Apparatus

FIG. 1 is a block diagram showing a configuration example of anelectronic apparatus including a solid-state imaging device to which anembodiment of the present disclosure is applied.

An electronic apparatus 1 is configured as a digital camera, a portableterminal having imaging capabilities, or the like, and is configured tocapture an image of an object with an autofocusing (AF) function togenerate a captured image, and store the image as a still image ormoving image. Hereinafter, the assumption is made that mainly a stillimage is recorded.

The electronic apparatus 1 includes a lens unit 11, an operating unit12, a controller 13, an image sensor 14, a signal processing unit 15, astorage unit 16, a display unit 17, a focus determination unit 18, and adriving unit 19.

The lens unit 11 is configured to collect light from an object (objectlight). The object light collected by the lens unit 11 enters the imagesensor 14.

The lens unit 11 includes a zoom lens 21, a diaphragm 22, and a focuslens 23.

The zoom lens 21 is configured to move in an optical axis direction bydriving of the driving unit 19, thereby changing the focal length toadjust the magnification of an object in a captured image. The diaphragm22 is configured to change the degree of opening by driving of thedriving unit 19, thereby adjusting the amount of object light to beincident on the image sensor 14. The focus lens 23 is configured to movein an optical axis direction by driving of the driving unit 19, therebyadjusting the focus.

The operating unit 12 is configured to receive a user's operation. Theoperating unit 12 supplies an operation signal to the controller 13 inthe case where a shutter button (not shown) is pressed, for example. Theoperation signal indicates that a shutter button is pressed.

The controller 13 is configured to control the operation of respectiveunits of the electronic apparatus 1.

For example, in the case where the controller 13 receives an operationsignal indicating that a shutter button is pressed, the controller 13supplies an instruction of recording a still image to the signalprocessing unit 15. In addition, the controller 13 supplies aninstruction of generating a live view image to the signal processingunit 15 to display the live view image on the display unit 17. The liveview image is a real-time image of an object.

In addition, the controller 13 supplies an instruction of performingfocus determining operation (phase difference detection operation) tothe signal processing unit 15 to determine focus with use of a phasedifference detection method. The phase difference detection method is afocus detection method in which light transmitted through an imaginglens is pupil-divided to form a pair of images, and the degree of focusis detected by measuring (detecting phase difference) the intervalbetween the formed images (amount of displacement between images).

The image sensor 14 is a solid-state imaging device configured tophotoelectrically convert received object light into an electric signal.

For example, the image sensor 14 is realized by a complementary metaloxide semiconductor (CMOS) image sensor, a charge coupled device (CCD)image sensor, or the like. In the case where the image sensor 14 is aCMOS image sensor, the image sensor 14 may be front-surface irradiationtype image sensor or rear-surface irradiation type image sensor. Inaddition, in the case where the image sensor 14 is a rear-surfaceirradiation type CMOS image sensor, the image sensor 14 may beconfigured as a lamination type CMOS image sensor in which asemiconductor substrate including a pixel array unit and a semiconductorsubstrate including a logic circuit are bonded together.

The image sensor 14 includes a pixel array unit in which a plurality ofpixels (imaging pixels) configured to generate a signal for generating acaptured image based on received object light, and a plurality of pixels(phase difference detection pixels) configured to generate a signal forperforming phase difference detection are arranged. The image sensor 14supplies an electric signal generated by photoelectric conversion to thesignal processing unit 15.

The signal processing unit 15 performs various types of signalprocessing on the electric signal supplied from the image sensor 14.

For example, in the case where an instruction of recording a still imageis supplied from the controller 13, the signal processing unit 15generates data of a still image (still image data) and supplies thegenerated data to the storage unit 16. In addition, in the case where aninstruction of generating a live view image is supplied from thecontroller 13, the signal processing unit 15 generates data of a liveview image (live view image data) based on a signal output from animaging pixel in the image sensor 14, and supplies the generated data tothe display unit 17.

In addition, in the case where an instruction of performing phasedifference detection operation is supplied from the controller 13, thesignal processing unit 15 generates data for detecting phase difference(phase difference detection data) based on a signal output from a phasedifference detection pixel in the image sensor 14, and supplies thegenerated data to the focus determination unit 18.

The storage unit 16 is configured to store the image data supplied fromthe signal processing unit 15. The storage unit 16 is configured as adisk such as a digital versatile disk (DVD), a semiconductor memory suchas a memory card, or one or more removable storage media, for example.These storage media may be built in the electronic apparatus 1, or maybe allowed to be mounted on and removed from the electronic apparatus 1.

The display unit 17 is configured to display an image based on the imagedata supplied from the signal processing unit 15. For example, in thecase where the live view image data is supplied from the signalprocessing unit 15, the display unit 17 displays a live view image. Thedisplay unit 17 is realized by a liquid crystal display (LCD), anelectro-luminescence (EL) display, or the like.

The focus determination unit 18 is configured to determine whether ornot an object being a focusing target (focusing target object) isfocused based on the phase difference detection data supplied from thesignal processing unit 15. In the case where an object in a focus areais focused, the focus determination unit 18 supplies, to the drivingunit 19, information representing that the object is focused as a focusdetermination result. In addition, in the case where the focus targetobject is not focused, the focus determination unit 18 calculates theamount of displacement of focus (defocus amount), and supplies, to thedriving unit 19, information representing the calculated defocus amountas a focus determination result.

The driving unit 19 is configured to drive the zoom lens 21, thediaphragm 22, and the focus lens 23. For example, the driving unit 19calculates the amount of driving of the focus lens 23 based on the focusdetermination result supplied from the focus determination unit 18, andmoves the focus lens 23 depending on the calculated driving amount.

Specifically, in the case where an object is focused, the driving unit19 causes the focus lens 23 to maintain the current position. Inaddition, in the case where an object is not focused, the driving unit19 calculates the driving amount (moving distance) based on the focusdetermination result representing the defocus amount and the position ofthe focus lens 23, and moves the focus lens 23 depending on the drivingamount.

Regarding Pixel Arrangement of Pixel Array Unit

Next, the pixel arrangement of the pixel array unit of the image sensor14 will be described with reference to FIG. 2.

As shown in FIG. 2, in the pixel array unit of the image sensor 14, aplurality of imaging pixels 31 represented by black squares aretwo-dimensionally arranged in a matrix pattern. The imaging pixel 31includes an R pixel, G pixel, and B pixel. These pixels are regularlyarranged in a Bayer pattern.

Moreover, in the pixel array unit of the image sensor 14, a plurality ofphase difference detection pixels 32 represented by white squares arearranged in a scattered pattern among the plurality of imaging pixels 31two-dimensionally arranged in a matrix pattern. Specifically, the phasedifference detection pixels 32 are regularly arranged in a specificpattern by replacing a part of the imaging pixels 31 in the pixel arrayunit of the image sensor 14. It should be noted that the arrangement ofthe imaging pixels 31 and the phase difference detection pixels 32 inthe image sensor 14 is not limited to the above, and the pixels may bearranged in another pattern.

Detailed Configuration Example of Pixel

FIG. 3 shows a detailed configuration example of the imaging pixel 31and the phase difference detection pixel 32 arranged in the pixel arrayunit.

As shown in FIGS. 3A and 3B, the imaging pixel 31 includes aphotoelectric conversion unit (photodiode) 41.

In the imaging pixel 31, a signal for generating a captured image isgenerated based on charges generated by photoelectric conversion ofreceived object light performed by the photoelectric conversion unit 41.

Moreover, although not shown, the imaging pixel 31 at least includes atransfer transistor that transfers charges stored in the photoelectricconversion unit 41, a floating diffusion (FD) that stores the chargestransferred from the photoelectric conversion unit 41 and converts thestored charges into voltage, a reset transistor that discharges (resets)charges stored in the FD, and an amplification transistor that amplifiesthe voltage of the FD and outputs the amplified voltage to a verticalsignal line. It should be noted that a selection transistor may beprovide between the amplification transistor and the vertical signalline. The selection transistor switches on and off of the output of thevoltage of the amplification transistor to the vertical signal line.

On the other hand, the phase difference detection pixel 32 includes twophotoelectric conversion units 42A and 42B. In the phase differencedetection pixel 32, a signal for performing phase difference detectionis generated based on charges generated by photoelectric conversion ofreceived object light performed by the photoelectric conversion units42A and 42B.

Moreover, although not shown, the phase difference detection pixel 32includes two transfer transistors, two FDs, two reset transistors, andtwo amplification transistors corresponding to the photoelectricconversion units 42A and 42B.

Specifically, the photoelectric conversion units 42A and 42B share theFD, the reset transistor, and the amplification transistor with thephotoelectric conversion unit 41 of the imaging pixel 31 adjacent to thephase difference detection pixel 32.

For example, as shown by broken lines a in FIG. 3A, the photoelectricconversion unit 42A can share the FD, the reset transistor, and theamplification transistor with the photoelectric conversion unit 41 theimaging pixel 31 adjacent to the phase difference detection pixel 32 onthe lower side. On the other hand, as shown by broken lines b in FIG.3A, the photoelectric conversion unit 42B can share the FD, the resettransistor, and the amplification transistor with the photoelectricconversion unit 41 of the imaging pixel 31 adjacent to the phasedifference detection pixel 32 on the right side.

Moreover, as shown by broken lines c in FIG. 3B, the photoelectricconversion unit 42A can share the FD, the reset transistor, and theamplification transistor with the photoelectric conversion unit 41 ofthe imaging pixel 31 adjacent to the phase difference detection pixel 32on the lower side. On the other hand, as shown by broken lines d in FIG.3B, the photoelectric conversion unit 42B can share the FD, the resettransistor, and the amplification transistor with the photoelectricconversion unit 41 of the imaging pixel 31 adjacent to the phasedifference detection pixel 32 on the upper side.

As described above, because the two photoelectric conversion units 42Aand 42B share the FD and the amplification transistor with differentadjacent pixels in the phase difference detection pixel 32, the imagesensor 14 can perform exposure (storing charges) of the twophotoelectric conversion units 42A and 42B, and read a signalcorresponding to the stored charges simultaneously.

Now, an embodiment in which the photoelectric conversion units 42A and42B share the FD, the reset transistor, and the amplification transistorwith the photoelectric conversion unit 41 of the adjacent imaging pixel31 will be described.

Configuration Example of First Embodiment

First, a configuration example of an imaging pixel and a phasedifference detection pixel according to a first embodiment of thepresent disclosure will be described with reference to FIGS. 4 and 5.FIG. 4 is a plan view showing a configuration example of the imagingpixel and the phase difference detection pixel, and FIG. 5 is a circuitdiagram showing a configuration example of the imaging pixel and thephase difference detection pixel.

In FIGS. 4 and 5, three imaging pixels 31Gr, 31Gb, and 31R, and thephase difference detection pixel 32 are shown.

In this example, the phase difference detection pixel 32 and the imagingpixel 31Gr form the configuration in which two vertical pixels areshared, and the imaging pixel 31Gb and the imaging pixel 31R form theconfiguration in which two vertical pixels are shared.

Each of the imaging pixels 31Gr, 31Gb, and 31R includes thephotoelectric conversion unit 41, a transfer transistor 51, an FD 52, areset transistor 53, an amplification transistor 54, a selectiontransistor 55, and an overflow control transistor 56 that dischargescharges stored in the photoelectric conversion unit 41.

By providing the overflow control transistor 56 in the imaging pixels31Gr, 31Gb, and 31R, it is possible to maintain the optical symmetrybetween pixels and to reduce the difference of the imaging properties.Furthermore, by switching on the overflow control transistor 56, it ispossible to suppress the blooming of adjacent pixel.

Moreover, the phase difference detection pixel 32 includes thephotoelectric conversion units 42A and 42B, the transfer transistor 51,the FD 52, the reset transistor 53, the amplification transistor 54, andthe selection transistor 55 corresponding to the photoelectricconversion units 42A and 42B.

It should be noted that the FD 52 corresponding to the photoelectricconversion unit 42B is shared with the photoelectric conversion unit 41of the imaging pixel 31Gb.

Furthermore, as shown in FIG. 4, the FD 52 corresponding to thephotoelectric conversion unit 42A in the phase difference detectionpixel 32 and the FD 52 of the imaging pixel 31Gr are connected to gateelectrodes of the amplification transistor 54 with respective wiringsFDL. Accordingly, the photoelectric conversion unit 42A can share the FD52, the amplification transistor 54, and the selection transistor 55with the photoelectric conversion unit 41 of the imaging pixel 31Gr.

Moreover, the FD 52 corresponding to the photoelectric conversion unit42B in the phase difference detection pixel 32 (i.e., the FD 52 of theimaging pixel 31Gb) and the FD 52 of the imaging pixel 31R are connectedto gate electrodes of the amplification transistor 54 with respectivewirings FDL. Accordingly, the photoelectric conversion unit 42B canshare the FD 52, the amplification transistor 54, and the selectiontransistor 55 with the photoelectric conversion unit 41 of the imagingpixels 31Gb and 31R.

According to the above configuration, because two photoelectricconversion units share an FD and an amplification transistor ofdifferent adjacent pixels in a phase difference detection pixel, it ispossible to simultaneously expose and read from the two photoelectricconversion units without providing a charge storage unit and to improveAF speed and accuracy.

Another Configuration Example of First Embodiment

Next, another configuration example of an imaging pixel and a phasedifference detection pixel according to the first embodiment of thepresent disclosure will be described with reference to FIGS. 6 and 7.FIG. 6 is a plan view showing a configuration example of the image pixeland the phase difference detection pixel, and FIG. 7 is a circuitdiagram showing a configuration example of the imaging pixel and thephase difference detection pixel.

It should be noted that between the imaging pixel 31Gb, 31Gr, and 31Rand the phase difference detection pixel 32 shown in FIGS. 6 and 7, andthe imaging pixel 31Gb, 31Gr, and 31R and the phase difference detectionpixel 32 shown in FIGS. 4 and 5, a description of components formed inthe same way will be omitted.

The imaging pixel 31Gr, 31Gb, and 31R and the phase difference detectionpixel 32 shown in FIGS. 6 and 7 include two conversion efficiencyswitching transistors 58 for each pixel sharing unit in addition to thecomponents shown in FIGS. 4 and 5. Specifically, the imaging pixel 31Gr,31Gb, and 31R and the FDs 52 in the phase difference detection pixel 32are connected to respective conversion efficiency switching transistors58.

In the pixel sharing unit (e.g., two pixels of the phase differencedetection pixel 32 and the imaging pixel 31Gr), when any one of the twoconversion efficiency switching transistors 58 is turned on, the oneconversion efficiency switching transistor 58 is electrically connectedto the FD 52. As a result, a floating diffusion area of the FD 52 isenlarged, the capacity of the FD 52 increases, and the conversionefficiency is reduced. Moreover, when the two conversion efficiencyswitching transistors 58 are turned on, the floating diffusion area ofthe FD 52 is further enlarged, and the conversion efficiency is furtherreduced.

As described above, because the conversion efficiency of the FD 52 canbe switched by turning on and off of the conversion efficiency switchingtransistor 58, it is possible to improve the signal to noise (S/N) ratioby turning off of the two conversion efficiency switching transistors 58and increasing the conversion efficiency under low illumination, and theFD 52 can receive the saturation amount of signals from thephotoelectric conversion unit 41 (42A and 42B) by turning on theconversion efficiency switching transistor 58 under high illumination.

Configuration Example of Second Embodiment

Next, a configuration example of an imaging pixel and a phase differencepixel according to a second embodiment of the present disclosure will bedescribed with reference to FIGS. 8 and 9. FIG. 8 is a plan view showinga configuration example of the imaging pixel and the phase differencepixel, and FIG. 9 is a circuit diagram showing a configuration exampleof the imaging pixel and the phase difference pixel.

In FIGS. 8 and 9, one imaging pixel 31 and one phase differencedetection pixel 32 are shown.

In this example, the phase difference detection pixel 32 and the imagingpixel 31 form the configuration in which two vertical pixels are shared.

The imaging pixel 31 includes the photoelectric conversion unit 41, thetransfer transistor 51, a transfer transistor 51D, the FD 52, the resettransistor 53, the amplification transistor 54, and the selectiontransistor 55. It should be noted that the transfer transistor 51D isprovided to maintain the symmetry of the pixel structure, and does nothave a function such as transferring charges of the photoelectricconversion unit 41 unlike the transfer transistor 51. It should be notedthat in the imaging pixel 31, an overflow control transistor thatdischarges charges stored in the photoelectric conversion unit 41 may beprovided.

Moreover, the phase difference detection pixel 32 includes thephotoelectric conversion units 42A and 42B, the transfer transistor 51,the FD 52, the reset transistor 53, the amplification transistor 54, andthe selection transistor 55 corresponding to the photoelectricconversion units 42A and 42B.

It should be noted that the FD corresponding to the photoelectricconversion unit 42B is shared with a photoelectric conversion unit of animaging pixel (not shown) adjacent to the phase difference detectionpixel 32.

Furthermore, as shown in FIG. 8, the FD 52 corresponding to thephotoelectric conversion unit 42A in the phase difference detectionpixel 32 and the FD 52 of the imaging pixel 31 are connected to gateelectrodes of the amplification transistor 54 with respective wiringsFDL. Accordingly, the photoelectric conversion unit 42A can share the FD52, the amplification transistor 54, and the selection transistor 55with the photoelectric conversion unit 41 of the imaging pixel 31.

Moreover, the FD 52 corresponding to the photoelectric conversion unit42B in the phase difference detection pixel 32 and an FD of the imagingpixel (not shown) are connected to gate electrodes an amplificationtransistor of the imaging pixel (not shown) with respective wirings FDL(not shown). Accordingly, the photoelectric conversion unit 42B canshare the FD, the amplification transistor, and the selection transistorwith the photoelectric conversion unit of the imaging pixel (not shown).

According to the above configuration, because two photoelectricconversion units share an FD and an amplification transistor ofdifferent adjacent pixels in the phase difference detection pixel, it ispossible to simultaneously expose and read from the two photoelectricconversion units without providing a charge storage unit and to improveAF speed and accuracy.

It should be noted that in this example, between pixels forming thepixel sharing unit (the imaging pixel 31 and the phase differencedetection pixel 32), a pixel transistor including the amplificationtransistor 54 is arranged. With such a configuration, as shown in FIG.10, which is an enlarged view of a part surrounded by broken lines e inFIG. 8, because the FD 52 of the respective pixels and the amplificationtransistor 54 are arranged to be adjacent to each other, it is possibleto design the length of the wiring FDL for connecting the FD 52 and theamplification transistor 54 to be short and to increase the conversionefficiency.

Furthermore, in this example, the source of the respective resettransistors 53 of the imaging pixel 31 and the phase differencedetection pixel 32 is connected to the FD 52 of the respective pixels.Accordingly, it is possible to reduce the capacity of the FD 52 and toincrease the conversion efficiency.

Furthermore, in this example, the drain of the respective resettransistors 53 of the imaging pixel 31 and the phase differencedetection pixel 32 is connected to a source of a conversion efficiencyswitching transistor 61. With such a configuration, it is possible tochange the capacity of the FD 52 by turning on and off of the resettransistor 53 of the respective pixels and to set the conversionefficiency.

Specifically, in the case where the respective reset transistors 53 ofthe imaging pixel 31 and the phase difference detection pixel 32 areturned on and the conversion efficiency switching transistor 61 isturned off in the state where the respective transfer transistors 51 ofthe imaging pixel 31 and the phase difference detection pixel 32 areturned on, the capacity of FD in the pixel sharing unit is the sum ofthe capacity of the FD 52 of the imaging pixel 31 and the capacity ofthe FD 52 of the phase difference detection pixel 32.

Moreover, in the case where the reset transistor 53 of any one of theimaging pixel 31 and the phase difference detection pixel 32 is turnedon and the conversion efficiency switching transistor 61 is turned offin the state where the respective transfer transistors 51 of the imagingpixel 31 and the phase difference detection pixel 32 are turned on, thecapacity of FD in the pixel sharing unit is the sum of the capacity ofthe FD 52 of the imaging pixel 31, the capacity of the FD 52 of thephase difference detection pixel 32, and the gate capacity and draincapacity of the turned-on reset transistor 53. Accordingly, it ispossible to reduce the conversion efficiency as compared with theabove-mentioned case.

Furthermore, in the case where the respective reset transistors 53 ofthe imaging pixel 31 and the phase difference detection pixel 32 areturned on and the conversion efficiency switching transistor 61 isturned off in the state where the respective transfer transistors 51 ofthe imaging pixel 31 and the phase difference detection pixel 32 areturned on, the capacity of FD in the pixel sharing unit is the sum ofthe capacity of the FD 52 of the imaging pixel 31, the capacity of theFD 52 of the phase difference detection pixel 32, and the gate capacityand drain capacity of the respective reset transistors 53 of the imagingpixel 31 and the phase difference detection pixel 32. Accordingly, it ispossible to further reduce the conversion efficiency as compared withthe above-mentioned case.

It should be noted that in the case where the respective resettransistors 53 of the imaging pixel 31 and the phase differencedetection pixel 32 are turned on and the conversion efficiency switchingtransistor 61 is turned on, the charges stored in the FD 52 are reset.

Moreover, in this example, the FD 52 (source of the reset transistor 53)is formed to be surrounded by an element division area isolated byshallow trench isolation (STI).

FIG. 11 shows a cross-sectional view of a part of the FD 52 taking alongthe double headed arrow a-a′ of FIG. 10.

As shown in FIG. 11, the FD 52 is formed to be surrounded by elementdivision areas 62 that are isolated by STI and include SiO₂, forexample. Accordingly, it is possible to suppress the diffusion of the FD52 by the element division areas 62 and to define the FD line width withthe width between the element division areas 62. Therefore, it ispossible not only to improve the conversion efficiency by reducing thecapacity of the FD 52 but also to reduce the production variability(specifically, variability in the line width and overlapping withrespect to a resist in a channel implant process when the FD 52 isformed).

Furthermore, in this example, as shown in FIG. 8, the transfertransistor 51 of each pixel is formed on a corner portion of eachphotoelectric conversion unit of each pixel, which is formed in arectangular shape. With such a configuration, the element division areain one pixel cell is reduced, and it is possible to enlarge the area ofthe photoelectric conversion unit. Therefore, it is possible toadvantageously perform designing from a viewpoint of a saturation amountof charge Qs even in the case where the photoelectric conversion unit isdivided into two parts in one pixel cell like the phase differencedetection pixel 32.

Configuration Example of Third Embodiment

Next, a configuration example of an imaging pixel and a phase differencedetection pixel according to a third embodiment of the presentdisclosure will be described with reference to FIGS. 12 and 13. FIG. 12is a plan view showing a configuration example of the imaging pixel andthe phase difference detection pixel, and FIG. 13 is a circuit diagramshowing a configuration example of the imaging pixel and the phasedifference detection pixel.

In FIGS. 12 and 13, three imaging pixels 31-1 to 31-3 and one phasedifference detection pixel 32 are shown.

In this example, the imaging pixel 31-1 and the imaging pixel 31-2 formthe configuration in which two vertical pixels are shared, and the phasedifference detection pixel 32 and the imaging pixel 31-3 form theconfiguration in which two vertical pixels are shared. Moreover, eachpixel sharing unit is arranged in a row adjacent to each other.

The imaging pixels 31-1 and 31-2 each include the photoelectricconversion unit 41 and the transfer transistor 51, and the photoelectricconversion units 41 share the FD 52, the reset transistor 53, theamplification transistor 54, and the selection transistor 55.

The imaging pixel 31-3 also includes the photoelectric conversion unit41 and the transfer transistor 51, and the phase difference detectionpixel 32 includes the photoelectric conversion units 42A and 42B, andthe respective transfer transistors 51 corresponding to thephotoelectric conversion units 42A and 42B. Then, the photoelectricconversion unit 41 of the imaging pixel 31-3 and the photoelectricconversion unit 42B of the phase difference detection pixel 32 share theFD 52, the reset transistor 53, the amplification transistor 54, and theselection transistor 55.

Moreover, the transfer transistor 51 corresponding to the photoelectricconversion unit 42A in the phase difference detection pixel 32 isconnected to a reading transistor 71 via the adjacent FD 52 and a wiringFDL.

The reading transistor 71 is formed between the FD 52 corresponding tothe photoelectric conversion unit 42A and the FD 52 shared by theimaging pixels 31-1 and 31-2. By turning on the reading transistor 71,the photoelectric conversion unit 42A shares the FD 52, theamplification transistor 54, and the selection transistor 55 with theimaging pixels 31-1 and 31-2 (i.e., pixels in adjacent row).

According to the above configuration, because two photoelectricconversion units share an FD and an amplification transistor ofdifferent adjacent pixels in the phase difference detection pixel, it ispossible to expose and read from the two photoelectric conversion unitswithout providing a charge storage unit and to improve AF speed andaccuracy.

It should be noted that in FIG. 12, a wiring FDL′ that connects thepixel sharing unit including the imaging pixels 31-1 and 31-2 and apixel transistor in an adjacent row on the upper side is provided tomaintain the symmetry with the wiring FDL that connects the transfertransistor 51 corresponding to the photoelectric conversion unit 42A anda pixel transistor in the pixel sharing unit including the imagingpixels 31-1 and 31-2.

In the above configuration, by turning on the reading transistor 71 whena signal for detecting phase difference is read, a signal correspondingto charges stored in the photoelectric conversion unit 42A is read froma pixel transistor in a pixel sharing unit including the imaging pixels31-1 and 31-2. A signal corresponding to charges stored in thephotoelectric conversion unit 42B is read from a pixel transistor in apixel sharing unit including the imaging pixel 31-3 and the phasedifference detection pixel 32. At this time, by turning on the readingtransistor 71 included in the respective pixel transistors, it ispossible to make the conversion efficiencies of the signals read fromthe photoelectric conversion units 42A and 42B equivalent to each other.

On the other hand, by turning off the reading transistor 71 when asignal for capturing an image is read, it is possible to maintain highconversion efficiency of an imaging pixel and to prevent the propertiesfrom being deteriorated. Moreover, in the case where the saturationamount of signals is beyond the range of FD, by turning on the readingtransistor 71, it is possible to reduce the conversion efficiency and toprevent charges in FD from overflowing. Specifically, in this case, thereading transistor 71 functions as a conversion efficiency switchingtransistor.

Furthermore, also in this example, as shown in FIG. 12, the transfertransistor 51 of each pixel is formed on a corner portion of thephotoelectric conversion unit of each pixel, which is formed in arectangular shape. With such a configuration, the element division areain one pixel cell is reduced, and it is possible to enlarge the area ofthe photoelectric conversion unit. Therefore, it is possible toadvantageously perform designing from a viewpoint of a saturation amountof charge Qs even in the case where the photoelectric conversion unit isdivided into two parts in one pixel cell like the phase differencedetection pixel 32.

Another Configuration Example of Third Embodiment

Next, another configuration example of an imaging pixel and a phasedifference detection pixel according to a third embodiment of thepresent disclosure will be described with reference to FIGS. 14 and 15.FIG. 14 is a plan view showing a configuration example of the imagingpixel and the phase difference detection pixel, and FIG. 15 is a circuitdiagram showing a configuration example of the imaging pixel and thephase difference detection pixel.

In FIGS. 14 and 15, seven imaging pixels 31-1 to 31-7 and one phasedifference detection pixel 32 are shown.

In this example, the imaging pixels 31-1 to 31-4, the phase differencedetection pixel 32, and the imaging pixels 31-5 to 31-7 form theconfiguration in which pixels are shared in a 2*2 matrix pattern.Moreover, each pixel sharing unit is arranged in a row adjacent to eachother.

The imaging pixels 31-1 to 31-4 each include the photoelectricconversion unit 41 and the transfer transistor 51, and the photoelectricconversion units 41 share the FD 52, the reset transistor 53, theamplification transistor 54, and the selection transistor 55.

The imaging pixels 31-5 to 31-7 also include the photoelectricconversion unit 41 and the transfer transistor 51, and the phasedifference detection pixel 32 includes the photoelectric conversionunits 42A and 42B and the transfer transistors 51 corresponding to thephotoelectric conversion units 42A and 42B. Then, the photoelectricconversion units 41 of the imaging pixels 31-5 to 31-7 share the FD 52,the reset transistor 53, the amplification transistor 54, and theselection transistor 55 with the photoelectric conversion unit 42B ofthe phase difference detection pixel 32.

Moreover, the transfer transistor 51 corresponding to the photoelectricconversion unit 42A in the phase difference detection pixel 32 isconnected to the reading transistor 71 via the adjacent FD 52 and thewiring FDL.

The reading transistor 71 is formed between the FD 52 corresponding tothe photoelectric conversion unit 42A and the FD 52 shared by theimaging pixels 31-1 to 31-4. By turning on the reading transistor 71,the photoelectric conversion unit 42A shares the FD 52, theamplification transistor 54, and the selection transistor 55 with theimaging pixels 31-1 to 31-4 (i.e., pixel in an adjacent row).

Also in the above configuration, because two photoelectric conversionunits share an FD and an amplification transistor of different adjacentpixels in a phase difference detection pixel, it is possible to exposeand read from the two photoelectric conversion units without providing acharge storage unit and to improve AF speed and accuracy.

It should be noted that in FIG. 14, a wiring FDL′ that connects thepixel sharing unit including the imaging pixels 31-1 and 31-4 and apixel transistor in an adjacent row on the upper side is provided tomaintain the symmetry with the wiring FDL that connects the transfertransistor 51 corresponding to the photoelectric conversion unit 42A anda pixel transistor in the pixel sharing unit including the imagingpixels 31-1 and 31-4.

It should be noted that although the phase difference detection pixelincludes two photoelectric conversion units in the above-mentionedembodiments, the number of photoelectric conversion units is not limitedto two, and the phase difference detection pixel may include three ormore photoelectric conversion units.

Embodiments of the present disclosure are not limited to theabove-mentioned embodiments and various modifications can be madewithout departing from the gist of the present disclosure.

Furthermore, the present disclosure may also take the followingconfigurations.

(1) A solid-state imaging device, including

a pixel array unit in which a plurality of imaging pixels configured togenerate an image, and a plurality of phase difference detection pixelsconfigured to perform phase difference detection are arranged, each ofthe plurality of phase difference detection pixels including

-   -   a plurality of photoelectric conversion units,    -   a plurality of floating diffusions configured to convert charges        stored in the plurality of photoelectric conversion units into        voltage, and    -   a plurality of amplification transistors configured to amplify        the converted voltage in the plurality of floating diffusions.        (2) The solid-state imaging device according to (1) above, in        which

in each of the plurality of phase difference detection pixels, at leastone of the plurality of photoelectric conversion units shares thefloating diffusion and the amplification transistor with at least one ofthe plurality of imaging pixels, which is adjacent to the phasedifference detection pixel.

(3) The solid-state imaging device according to (1) or (2) above, inwhich

the phase difference detection pixel includes a first photoelectricconversion unit and a second photoelectric conversion unit,

the first photoelectric conversion unit shares the floating diffusionand the amplification transistor with a first imaging pixel adjacent tothe phase difference detection pixel, and

the second photoelectric conversion unit shares the floating diffusionand the amplification transistor with a second imaging pixel that isdifferent from the first imaging pixel and is adjacent to the phasedifference detection pixel.

(4) The solid-state imaging device according to (3) above, in which

the phase difference detection pixel and the first imaging pixel areincluded in one pixel sharing unit, and

the second imaging pixel is included in another pixel sharing unit.

(5) The solid-state imaging device according to (4) above, in which

a pixel transistor including the amplification transistor is arrangedbetween pixels constituting the pixel sharing unit.

(6) The solid-state imaging device according to (4) or (5) above, inwhich

the pixel sharing unit includes

-   -   a reset transistor configured to discharge charges stored in        each of the floating diffusions in the pixels constituting the        pixel sharing unit, and    -   a conversion efficiency switching transistor that is connected        to the reset transistor and is configured to change capacity of        the floating diffusion in each of the pixels constituting the        pixel sharing unit.        (7) The solid-state imaging device according to (6) above, in        which    -   a source of the reset transistor is connected to the floating        diffusion in each of the pixels constituting the pixel sharing        unit, and    -   a drain of the reset transistor is connected to a source of the        conversion efficiency switching transistor.        (8) The solid-state imaging device according to any one of (4)        to (7) above, in which

the floating diffusion is formed surrounded by an element division areaisolated by shallow trench isolation.

(9) The solid-state imaging device according to (4) above, in which

the pixel sharing unit including the second imaging pixel is arranged ina row adjacent to the pixel sharing unit including the phase differencedetection pixel and the first imaging pixel.

(10) The solid-state imaging device according to (9) above, in which

between the floating diffusion corresponding to the second photoelectricconversion unit and the floating diffusion of the second imaging pixel,a reading transistor configured to read charges stored in the secondphotoelectric conversion unit is formed.

(11) The solid-state imaging device according to any one of (4) to (10)above, in which

each of the pixels includes a transfer transistor configured to transfercharges stored in the photoelectric conversion unit to the floatingdiffusion, and

the transfer transistor is formed on a corner portion of thephotoelectric conversion unit formed in a rectangular shape.

(12) The solid-state imaging device according to any one of (4) to (11),in which

the pixel sharing unit shares two pixels arranged vertically.

(13) The solid-state imaging device according to (4) to (11) above, inwhich

the pixel sharing unit shares pixels arranged in a 2*2 matrix pattern.

(14) A method for driving a solid-state imaging device that includes apixel array unit in which a plurality of imaging pixels configured togenerate an image, and a plurality of phase difference detection pixelsconfigured to perform phase difference detection are arranged, each ofthe plurality of phase difference detection pixels including a pluralityof photoelectric conversion units, a plurality of floating diffusionsconfigured to convert charges stored in the plurality of photoelectricconversion units into voltage, and a plurality of amplificationtransistors configured to amplify the converted voltage in the pluralityof floating diffusions, the method including:

storing charges in the plurality of photoelectric conversion units; and

reading signals corresponding to the charges stored in the plurality ofphotoelectric conversion units, by the solid-state imaging device, inthe phase difference detection pixel.

(15) An electronic apparatus, including

a solid-state imaging device that includes a pixel array unit in which aplurality of imaging pixels configured to generate an image, and aplurality of phase difference detection pixels configured to performphase difference detection are arranged, each of the plurality of phasedifference detection pixels including

-   -   a plurality of photoelectric conversion units,    -   a plurality of floating diffusions configured to convert charges        stored in the plurality of photoelectric conversion units into        voltage, and    -   a plurality of amplification transistors configured to amplify        the converted voltage in the plurality of floating diffusions.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An imaging device, comprising: a pixel array unitincluding a plurality of imaging pixels configured to generate an imageand a plurality of phase difference detection pixels configured toperform phase difference detection, each of the plurality of phasedifference detection pixels including: a plurality of photoelectricconversion units, a plurality of floating diffusions configured toconvert charges stored in the plurality of photoelectric conversionunits into voltage, a plurality of amplification transistors configuredto amplify the converted voltage in the plurality of floatingdiffusions; and a plurality of conversion efficiency switchingtransistors, wherein, at least one phase difference detection pixel ofthe plurality of phase difference detection pixels includes a firstphotoelectric conversion unit and a second photoelectric conversionunit, the first photoelectric conversion unit sharing a first floatingdiffusion and a first amplification transistor with a first imagingpixel adjacent to the at least one phase difference detection pixel ofthe plurality of phase difference detection pixels, the secondphotoelectric conversion unit sharing a second floating diffusion and asecond amplification transistor with a second imaging pixel and a thirdimaging pixel that are different from the first imaging pixel and areadjacent to the at least one phase difference detection pixel of theplurality of phase difference detection pixels, and a first conversionefficiency switching transistor is coupled to the first floatingdiffusion and second and third conversion efficiency switchingtransistors of the plurality of conversion efficiency switchingtransistors are electrically coupled to the second floating diffusion,each of the first, second, and third conversion efficiency switchingtransistors being configured to change a capacity of the respectivefirst or second floating diffusion.
 2. The imaging device according toclaim 1, wherein the at least one of the plurality of phase differencedetection pixels and the first imaging pixel are included in a firstpixel sharing unit, and the second imaging pixel is included in a secondpixel sharing unit.
 3. The imaging device according to claim 2, whereinthe first pixel sharing unit includes: a reset transistor configured todischarge charges stored in the first floating diffusion, and the firstconversion efficiency switching transistor of the plurality ofconversion efficiency switching transistors is coupled to the resettransistor.
 4. The imaging device according to claim 3, wherein a sourceof the reset transistor is coupled to the first floating diffusion, anda drain of the reset transistor is coupled to a source of the firstconversion efficiency switching transistor.
 5. The imaging deviceaccording to claim 2, wherein the first floating diffusion is formedsurrounded by an element division area isolated by shallow trenchisolation.
 6. The imaging device according to claim 2, wherein thesecond pixel sharing unit including the second imaging pixel is arrangedin a row adjacent to the first pixel sharing unit including the phasedifference detection pixel and the first imaging pixel.
 7. The imagingdevice according to claim 6, wherein between the second floatingdiffusion corresponding to the second photoelectric conversion unit andthe first floating diffusion of the first imaging pixel, a readingtransistor configured to read charges stored in the second photoelectricconversion unit is formed.
 8. The imaging device according to claim 2,wherein each of the first, second, and third imaging pixels include atransfer transistor configured to transfer charges stored in thephotoelectric conversion unit of the respective imaging pixel to therespective floating diffusion, and each transfer transistor is formed ona corner portion of the respective photoelectric conversion unit formedin a rectangular shape.
 9. The imaging device according to claim 2,wherein the first pixel sharing unit shares two pixels arrangedvertically.
 10. The imaging device according to claim 2, wherein thefirst pixel sharing unit shares pixels arranged in a 2×2 matrix pattern.11. The imaging device according to claim 1, wherein each imaging pixelof the plurality of imaging pixels includes an overflow transistorconfigured to discharge charges stored in photoelectric conversion unitsof the respective imaging pixel.
 12. The imaging device according toclaim 1, further comprising: a first overflow transistor coupled to thefirst imaging pixel; a second overflow transistor coupled to the secondimaging pixel; and a third overflow transistor coupled to the thirdimaging pixel, wherein, each of the first, second, and third overflowtransistors are configured to discharge charges stored in photoelectricconversion units corresponding to the respective first, second, andthird imaging pixels.
 13. A method for driving an imaging device thatincludes a pixel array unit including a plurality of imaging pixelsconfigured to generate an image and a plurality of phase differencedetection pixels configured to perform phase difference detection, eachof the plurality of phase difference detection pixels including aplurality of photoelectric conversion units, a plurality of floatingdiffusions configured to convert charges stored in the plurality ofphotoelectric conversion units into voltage, a plurality ofamplification transistors configured to amplify the converted voltage inthe plurality of floating diffusions, and a plurality of conversionefficiency switching transistors, at least one phase differencedetection pixel of the plurality of phase difference detection pixelsincluding a first photoelectric conversion unit and a secondphotoelectric conversion unit, the first photoelectric conversion unitsharing a first floating diffusion and a first amplification transistorwith a first imaging pixel adjacent to the at least one phase differencedetection pixel of the plurality of phase difference detection pixels,the second photoelectric conversion unit sharing a second floatingdiffusion and a second amplification transistor with a second imagingpixel and a third imaging pixel that are different from the firstimaging pixel and are adjacent to the at least one phase differencedetection pixel of the plurality of phase difference detection pixels,and a first conversion efficiency switching transistor is electricallycoupled to the first floating diffusion and second and third conversionefficiency switching transistors of the plurality of conversionefficiency switching transistors are coupled to the second floatingdiffusion, each of the first, second, and third conversion efficiencyswitching transistors being configured to change a capacity of therespective first or second floating diffusion, the method comprising:storing charges in the plurality of photoelectric conversion units; andreading signals corresponding to the charges stored in the plurality ofphotoelectric conversion units, by the imaging device, in the at leastone phase difference detection pixel of the plurality of phasedifference detection pixels.
 14. An electronic apparatus, comprising animaging device that includes a pixel array unit including a plurality ofimaging pixels configured to generate an image and a plurality of phasedifference detection pixels configured to perform phase differencedetection, each of the plurality of phase difference detection pixelsincluding: a plurality of photoelectric conversion units, a plurality offloating diffusions configured to convert charges stored in theplurality of photoelectric conversion units into voltage, a plurality ofamplification transistors configured to amplify the converted voltage inthe plurality of floating diffusions, and a plurality of conversionefficiency switching transistors, wherein, at least one phase differencedetection pixel of the plurality of phase difference detection pixelsincludes a first photoelectric conversion unit and a secondphotoelectric conversion unit, the first photoelectric conversion unitsharing a first floating diffusion and a first amplification transistorwith a first imaging pixel adjacent to the at least one phase differencedetection pixel of the plurality of phase difference detection pixels,the second photoelectric conversion unit sharing a second floatingdiffusion and a second amplification transistor with a second imagingpixel and a third imaging pixel that are different from the firstimaging pixel and are adjacent to the at least one phase differencedetection pixel of the plurality of phase difference detection pixels,and a first conversion efficiency switching transistor is coupled to thefirst floating diffusion and second and third conversion efficiencyswitching transistors of the plurality of conversion efficiencyswitching transistors are electrically coupled to the second floatingdiffusion, each of the first, second, and third conversion efficiencyswitching transistors being configured to change a capacity of therespective first or second floating diffusion.